Geometrical magnetic frustration in rare-earth chalcogenide spinels

We have characterized the magnetic and structural properties of the CdLn{sub 2}Se{sub 4} (Ln=Dy,Ho), and CdLn{sub 2}S{sub 4} (Ln=Ho,Er,Tm,Yb), spinels. We observe all compounds to be normal spinels, possessing a geometrically frustrated sublattice of lanthanide atoms with no observable structural disorder. Fits to the high-temperature magnetic susceptibilities indicate these materials to have effective antiferromagnetic interactions, with Curie-Weiss temperatures {theta}{sub W}{approx}-10 K, except CdYb{sub 2}S{sub 4} for which {theta}{sub W}{approx}-40 K. The absence of magnetic long-range order or glassiness above T=1.8 K strongly suggests that these materials are a different venue in which to study the effects of strong geometrical frustration, potentially as rich in interesting physical phenomena as that of the pyrochlore oxides.